#ifndef _BLK_H_
#define _BLK_H_

#define NR_BLK_DEV 7
/*
 * NR_REQUEST is the number of entries in the request-queue.
 * NOTE that writes may use only the low 2/3 of these: reads
 * take precedence.
 *
 * 32 seems to be a reasonable number: enough to get some benefit
 * from the elevator-mechanism, but not so much as to lock a lot of
 * buffers when they are in the queue. 64 seems to be too many (easily
 * long pauses in reading when heavy writing/syncing is going on)
 */
#define NR_REQUEST 32

/*
 * Ok, this is an expanded form so that we can use the same
 * request for paging requests when that is implemented. In
 * paging, 'bh' is NULL, and 'waiting' is used to wait for
 * read/write completion.
 */
struct request {
    int dev; /* -1 if no request */
    int cmd; /* READ or WRITE */
    int errors;
    unsigned long sector;
    unsigned long nr_sectors;
    char *buffer;
    struct task_struct *waiting;
    struct buffer_head *bh;
    struct request *next;
};

/*
 * This is used in the elevator algorithm: Note that
 * reads always go before writes. This is natural: reads
 * are much more time-critical than writes.
 */
#define IN_ORDER(s1, s2) \
    ((s1)->cmd < (s2)->cmd || ((s1)->cmd == (s2)->cmd && \
                               ((s1)->dev < (s2)->dev || ((s1)->dev == (s2)->dev && \
                                                          (s1)->sector < (s2)->sector))))

struct blk_dev_struct {
    void (*request_fn)(void);
    struct request *current_request;
};

extern struct blk_dev_struct blk_dev[NR_BLK_DEV];
extern struct request request[NR_REQUEST];
extern struct task_struct *wait_for_request;

#ifdef MAJOR_NR

/*
 * Add entries as needed. Currently the only block devices
 * supported are hard-disks and floppies.
 */

#if (MAJOR_NR == 1)
/* ram disk */
#define DEVICE_NAME       "ramdisk"
#define DEVICE_REQUEST    do_rd_request
#define DEVICE_NR(device) ((device)&7)
#define DEVICE_ON(device)
#define DEVICE_OFF(device)

#elif (MAJOR_NR == 2)
/* floppy */
#define DEVICE_NAME        "floppy"
#define DEVICE_INTR        do_floppy
#define DEVICE_REQUEST     do_fd_request
#define DEVICE_NR(device)  ((device)&3)
#define DEVICE_ON(device)  floppy_on(DEVICE_NR(device))
#define DEVICE_OFF(device) floppy_off(DEVICE_NR(device))

#elif (MAJOR_NR == 3)
/* harddisk */
#define DEVICE_NAME       "harddisk"
#define DEVICE_INTR       do_hd
#define DEVICE_REQUEST    do_hd_request
#define DEVICE_NR(device) (MINOR(device) / 5)
#define DEVICE_ON(device)
#define DEVICE_OFF(device)

#elif
/* unknown blk device */
#error "unknown blk device"

#endif

#define CURRENT     (blk_dev[MAJOR_NR].current_request)
#define CURRENT_DEV DEVICE_NR(CURRENT->dev)

#ifdef DEVICE_INTR
void (*DEVICE_INTR)(void) = NULL;
#endif
static void(DEVICE_REQUEST)(void);

static inline void unlock_buffer(struct buffer_head *bh) {
    if (!bh->b_lock)
        printk(DEVICE_NAME ": free buffer being unlocked\n");
    bh->b_lock = 0;
    wake_up(&bh->b_wait);
}

static inline void end_request(int uptodate) {
    DEVICE_OFF(CURRENT->dev);
    if (CURRENT->bh) {
        CURRENT->bh->b_uptodate = uptodate;
        unlock_buffer(CURRENT->bh);
    }
    if (!uptodate) {
        printk(DEVICE_NAME " I/O error\n\r");
        printk("dev %04x, block %d\n\r", CURRENT->dev,
               CURRENT->bh->b_blocknr);
    }
    wake_up(&CURRENT->waiting);
    wake_up(&wait_for_request);
    CURRENT->dev = -1;
    CURRENT = CURRENT->next;
}

#define INIT_REQUEST \
    repeat: \
    if (!CURRENT) \
        return; \
    if (MAJOR(CURRENT->dev) != MAJOR_NR) \
        panic(DEVICE_NAME ": request list destroyed"); \
    if (CURRENT->bh) { \
        if (!CURRENT->bh->b_lock) \
            panic(DEVICE_NAME ": block not locked"); \
    }

#endif

#endif
